Gulf oil dispersant hung around for months

Emma Woollacott, 27th January 2011

Much of the dispersant used to combat last year’s Deepwater Horizon oil spill still hadn't degraded months after it was applied.

Nearly 800,000 gallons of chemical dispersant were injected directly into the oil and gas flow coming out of the wellhead nearly a mile deep in the Gulf of Mexico.

But while research from the Woods Hole Oceanographic Institution (WHOI) suggests that the dispersant did mingle with the oil and gas flowing from the wellhead, it seems that a major component of the dispersant was contained within an oil-gas-laden plume in the deep ocean and had still not degraded some three months later.

The findings raise questions, says the team, about what impact the eep-water residue of oil and dispersant — which many believe has its
own toxic effects — might have had on the environment and marine life in the Gulf.

"This study gives our colleagues the first environmental data on the fate of dispersants in the spill. These data will form the basis of toxicity studies and modeling studies that can assess the efficacy and impact of the dispersants," says WHOI chemist Elizabeth B Kujawinski.

"We don’t know if the dispersant broke up the oil. We found that it didn’t go away, and that was somewhat surprising."

Though the mixture may or may not be toxic, she says, it warrants examination for possible effects on corals and deep-water fish.

"The decision to use chemical dispersants at the sea floor was a classic choice between bad and worse," says David Valentine of UC Santa Barbara.

"And while we have provided needed insight into the fate and transport of the dispersant we still don’t know just how serious the threat is; the deep ocean is a sensitive ecosystem unaccustomed to chemical irruptions like this, and there is a lot we don’t understand about this cold, dark world."